Heretofore, most systems for providing pictorial information within the view of an observer required relatively large and bulky equipment. Typical of such early systems are those utilizing a cathode ray tube with the information displayed thereon transmitted to an observer by means of a partial reflective surface positioned within the normal viewing field of the observer. One such system is described in U.S. Pat. No. 3,666,887 issued to Michael H. Freeman. With early personal display devices where a fixed composite display was presented, there was required a restricted movement of the observer's head thereby restricting vision of the environment to one direction. These types of systems, in addition to being expensive and bulky, restricts the observer's normal binocular vision and limits the viewing of the surroundings to one direction.
Another implementation of a system for superimposing an image on the normal background environment of an observer utilized a miniaturized cathode ray tube supported on the side of the observer's head with the display image reflected to the observer by means of corrective or plain lenses of conventional eyewear. The observer sees a picture from the cathode ray tube, as well as being able to see normally through lenses of the conventional eyewear.
Although there are many applications which require an observer to scan a screen displaying pictorial information, which may be constantly changing, in addition to maintaining continual visual awareness of the normal surroundings, the invention herein claimed will be described with emphasis directed to a vehicle operator as the observer. For example, in many situations the pilot of an aircraft must maintain visual awareness of conditions surrounding the aircraft in addition to viewing a display showing attitude or altitude of the aircraft.
When flying an aircraft at very low altitudes, where conditions change rapidly, the pilot cannot give sufficient attention to both the surrounding environment and visual displays if he is required to move his head to view the surrounding environment and the displays. Normally it takes several seconds for the pilot's eyes to refocus from the relatively short distances encountered when viewing the displays and the relatively long distances when viewing surrounding environment. The result is that the observer (pilot of an aircraft) is unable to give the required full attention to the displays and the surrounding environment.
Although the invention will be described with reference to operation of an aircraft by a pilot, it should be understood that the invention also finds utility in speech interpretation assistance as part of a device as described in U.S. Pat. No. 3,936,605. The utility for the device such as described in U.S. Pat. No. 3,936,605 for speech interpretation assistance is set out in U.S. Pat. No. 3,463,885.